Sorry for this rather embarrassing question, but I wondered what button you press to actually 'spot' an opponent??

Many thanks.

Up on the D pad to get your visor on, then press X whilst looking at an enemy player. =)

I forgot to mention that whilst in visor mode you can press LT to zoom in.

You don't need to push 'X' to actually spot them. You just have to view them through the visor and focus on them for 1 second.